The entire disclosure of Japanese Patent Application No 10-307,659 filed on Oct. 28, 1998, including specification, claims, drawings and summary is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a riparian improvement structure unit and, more particularly, to a riparian improvement structure unit to be laid in a river, lake or sea, etc., or at the shore or ridge thereof, upon embankment construction for foot protection, river protection, breaking of water, water stream control, etc. Moreover, the present invention relates to such a riparian improvement structure unit that provides a riparian area such as a riverbed bottom, shore, bank, etc. of a river, lake or sea, etc. with the surroundings suitable for habitation and/or growth of aquatic life.
2. Description of the Related Art
Riparian improvement construction work is being carried out in many cases with the major objects to protect the inhabitants of a riparian area of a river, lake or sea, etc. from flood, high tide, etc., in particular upon natural disasters, e.g., flood, etc. In order to achieve the object, the riparian improvement construction is implemented with the measures, for instance, to expand a water passage of a river, etc. or to make a meandering water channel straight so as to allow water to flow faster down to sea, lake, river, etc. and to flatten rapids or deep pool of a river, lake, sea, etc. so as to allow water to flow smoothly.
Conventional riparian improvement work has hitherto been implemented for foot protection, river protection, breaking of water, water stream control, etc. For conventional construction processes, wood materials composed of sticks, twigs, round timber, etc. or stone materials are mainly used. In modern conventional construction processes, concrete blocks, etc. have extensively been used.
The concrete block construction processes can provide the advantages of shortening a period of construction and withstanding a rapid water stream of a river, etc. at a sufficiently high level of resistance because they can prevent the earth and sand on the riverbed from being washed or carried away. This construction process, however, suffers from the drawbacks that concrete blocks change the ecological system of the riparian area and the place where they are laid is no longer inhabitable with aquatic life such as fish, crustaceans, e.g., crabs, shrimps, aquatic insects, etc. and suitable for the growth of aquatic plant, etc.
With the above background, the conventional construction processes that utilize natural materials, such as wooden materials, etc., have again been attracting attention, particularly in terms of providing the surroundings suitable for the habitation and/or growth of such aquatic life. These conventional construction processes utilizing wooden materials, however, had the technical problems that, although bundles of combinations of sticks, twigs, round timbers, etc. are laid on the bottom of a sea, lake, river or the like, spaces among the wooden materials of such bundles become almost flattened by a weight, such as stones, etc., placed thereon in order to prevent them from being carried away, and fresh water containing a sufficient amount of dissolved oxygen can little pass through the spaces so that aquatic life cannot live or grow in them any longer. In addition to these technical problems, they further have suffered from the growing difficulty of collecting wooden materials such as sticks, twigs, round timbers, etc. and have the problems that they require special skills for tightening sticks, twigs, round timbers, etc., into a whole constructed structure and, as a result, a period of construction becomes prolonged and construction costs are made expensive.
In order to solve the problems prevailing in the conventional construction processes, the present invention has the object to provide a riparian improvement structure unit for use upon foot protection, river protection, breaking of water, water control, and so on, which can improve the riparian area of a river, lake, sea, etc. as well as provide the riparian area with the surroundings suited for aquatic life to live in or grow.
Further, the present invention has the object to provide the riparian improvement structure unit suitable for the habitation and/or growth of aquatic life in the riparian area of a river, lake, sea, etc.
In order to achieve the object, the present invention provides a riparian improvement structure unit that can be disposed on the bottom or side of a riparian area of a sea, lake, rive, or the like, for foot protection, river-bed or bank protection, water breaking, water control, or the like, and that comprises: a first tubular member having a plurality of through holes on its sides; a plurality of stick-and-twig members disposed around the first tubular member; and a bundling member that winds and ties the plural stick-and-twig members and the first tubular member into a bundle.
As the riparian improvement structure units according to the present invention are laid on the bottom or sides of a riparian area in a sea, lake, river, or the like for foot protection, river-bed or river protection, etc., fresh water containing a sufficiently high amount of dissolved oxygen essential for aquatic life can be supplied into the inside of the riparian improvement structure units via the first tubular member. The fresh water supplied into the first tubular members is then allowed to pass through the holes formed round the sides of them into the inside of the stick-and-twig members wound and tied in bundles and to spread into a large number of gaps formed among the stick-and-twig member=the stick-and-twig members wound and tied in bundles around the first tubular member=the first tubular member. The fresh water supplied into the stick-and-twig members is then allowed to spread into a surrounding area in the vicinity of the riparian improvement structures, where structures and cobblestones, etc. are placed, and can provide the surroundings suitable for the habitation and growth of aquatic life.
The first tubular member may preferably be provided with a plurality of partition walls defining the inside into a plurality of inner spaces and each of the partition walls may preferably have an opening that communicates the adjacent inner spaces with each other. The provision of the openings among the partition walls can serve in smoothly flowing fresh water through the first tubular member over its entire length from one end to the other, and the inner spaces defined by the partition walls and communicating with each other via the openings disposed in the partition walls cause turbulence in the flow of water passing through the first tubular member, thereby increasing an amount of the water flowing out through the holes formed in the sides of the first tubular member into the surroundings.
The riparian improvement structure unit according to another embodiment of the present invention may preferably have a second tubular member disposed generally along and in parallel to the first tubular member and wound and tied into a bundle together with the stick-and-twig members and the first tubular member. The second tubular member likewise has substantially the same functions as the first tubular member and it permits a smooth passage of fresh water through the riparian improvement structure unit and a sufficient supply of fresh water into the surrounding area round the riparian improvement structure unit thereby providing the surroundings suitable for the habitation and growth of aquatic life.
In a preferred mode of the present invention, the first tubular member may comprise a tubular member made of a bamboo stem with joints. The partitions at the joints of the bamboo stem can act as partition walls of the first tubular member, and they are provided each with an opening to allow a passage and flow of water therein and therethrough over its entire length from one end to the other. The use of such a natural material, such as bamboo stems, etc., for the first tubular members can provide the surroundings suitable for the habitation and growth of aquatic life. Further, bamboo stems are rich in resources and very cheap in costs because bamboo grows annually and are cut every year. Moreover, the use of bamboo stems can present the advantage in the processing because the bamboo stems can be processed with ease and without difficulty so as to be adapted to the riparian improvement structure units for use with the present invention.
In the preferred mode of the riparian improvement structure units for which the second tubular member is used, the riparian improvement structure unit is configured such that the first tubular member or members is or are arranged in parallel to and along the second tubular member or members and the stick-and-twig members are disposed around the first and second tubular members, and that all the tubular members and the stick-and-twig members are wound and tied into a bundle with a bundling member or members.
In a preferred embodiment, the stick-and-twig member may be composed of a larger-sized stick-and-twig member and a smaller-sized stick-and-twig member and the smaller-sized stick-and-twig member is disposed around the first and second tubular members and the larger-sized stick-and-twig member in turn is disposed around a generally entire or partial circumference of the smaller-sized stick-and-twig member.
Other objects, features and advantages of the present invention become apparent in the course of the description that follows, with respect to the accompanying drawings.